1. Field of the Invention
An embodiment of the present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device capable of reducing a driving voltage and improving emission efficiency.
2. Description of the Related Art
An organic light emitting display device may be formed by a passive matrix method in which organic light emitting diodes (OLED) are coupled between scan lines and data lines in a matrix to form pixels and an active matrix method in which operations of pixels are controlled by thin film transistors (TFT) that function as switches. In general, the organic light emitting display device of the active matrix method includes TFTs for transmitting signals and capacitors for maintaining signals.
The OLED includes an anode electrode, a light emitting layer, and a cathode electrode. When a voltage is applied between the anode electrode and the cathode electrode, holes injected into the anode electrode and electrons injected into the cathode electrode are re-combined with each other in the light emitting layer to generate exitons and the generated exitons are transited to a base state to emit light. At this time, the emitted light may have different wavelengths, for example, red, green, and blue wavelengths in accordance with the light emitting layer. The wavelength of the emitted light may be determined by a material (an organic matter including a host material and a dopant material) of the light emitting layer.
Since OLEDs emit light by re-combination of the holes and the electrons, mobilities of the holes and the electrons are very important. For this purpose, the light emitting layer includes an injecting layer and a transport layer that facilitate movements of the holes and the electrons. It is however necessary to develop a technology of improving emission efficiency.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.